1. Field of the Invention
The present invention relates to a structure for transmitting the power of an engine in a motorcycle or the like and, in particular, to the structure in which an intermediate shaft is interposed between a crankshaft and the main input shaft of a transmission. The invention also relates to a process for assembling said structure.
2. Description of Background Art
A structure for transmitting the power of an engine using such an intermediate shaft is already publicly known and, for example, Japanese Examined Patent Publication No. 7-54134 discloses a structure in which an intermediate shaft driven gear and an intermediate shaft driving gear are disposed on an intermediate shaft and in which the intermediate shaft driven gear is engaged with the driving gear of a crankshaft inside a crankcase, and in which the intermediate driving gear is engaged with the input gear of the input shaft of a transmission outside the crankshaft, and in which a balancer weight is integrally formed inside the crankcase of the intermediate shaft.
Further, Japanese Examined Patent Publication No. 7-94859 discloses a power transmission structure in which an idle gear is arranged at the end portion projecting outside the crankcase of an intermediate shaft, and is engaged with both the driving gear of a crankshaft and the input gear of the input shaft of a transmission, which are disposed outside the crankcase.
In this connection, when an intermediate shaft driven gear and a intermediate shaft driving gear are disposed on an intermediate shaft inside and outside the crankcase, as disclosed in Japanese Examined Patent Publication No. 7-54134, many man hours are required for assembly. Thus, it would be desirable to improve workability of assembly. Further, if a balancer weight is mounted on the intermediate shaft inside the crankcase, restrictions are introduced into the layout, depending on the presence or absence of a clearance between the balancer web and a crank web. Therefore, it would be desirable to provide an improved structure capable of increasing the layout flexibility and of producing a greater balancing effect.
Further, if a gear disposed on the intermediate shaft is used only as an idle gear, as Japanese Examined Patent Publication No. 7-94859 discloses, a free speed reduction ratio cannot be obtained and the distance between the intermediate shaft and the input shaft of the transmission is inevitably made greater.
The object of the present invention is to solve these problems.